Figure 1

Four types of reaction carried out by nitrilase superfamily members. (a) The nitrilase reaction is performed by branch 1 enzymes. In plants, the substrate is indole-3-acetonitrile and the product is indole-3-acetic acid. (b) The amidase reaction is the most frequently observed activity in the superfamily. Branch 2-4 enzymes are amidases and nitrilase-related domains of branch 7 and 8 enzymes are proposed to be amidases specific for glutamine. (c) The carbamylase reaction is a special case of the amidase reaction, carried out by branch 5 and 6 enzymes. (d) Branch 9 N-acyltransferases perform the amidase reaction in reverse, transferring a fatty acid from phospholipid (not shown) to a polypeptide amino terminus. The polypeptide acceptor usually contains an amino-terminal diacylglyceride-modified cysteine (not shown). All nitrilase-related reactions are thought to proceed through acylenzyme intermediates.